We have investigated the effect of interface roughness on the operation of n-channel SOI MESFET device structure. Due to the presence of a rough interface between the buried oxide and the silicon layer, interface roughness scattering limits the velocity of the carriers at high transverse fields. Following Fischetti and Laux, we model interface roughness as a real space scattering event, separated into specular and diffusive (isotropic) type of reflection from an ideal interface. This model gives rise to low field silicon electron mobility in agreement with available experimental values. To examine the performance improvement of SOI devices, we have simulated analogous SOI MESFET and MOSFET device structures. The results of these investigations suggest that the mobility of the MOSFET device follows the experimental values and the mobility, of the MESFET is five to ten times higher than that of the MOSFET in the subthreshold and the on-state regime. (C) 2004 American Vacuum Society.